UV editor vert, edge and face selection modes as keybinds?
There is already a shortcut for the UV selection type menu, it is Ctrl+Tab.

After pressing Ctrl+Tab you can right-click on Vertex, Edge, Face or Island and choose Add Shortcut.

This is much easier than trying to do it via the key-bindings editor as you can see from the complexity of the new shortcut after it is added:



To make these new shortcuts appear in all files go to File> User Preferences> Save User Settings.